Incremental Analysis, With Two Yards to
Go

By DAVID
LEONHARDTPublished: February 1, 2004

HE academic paper that David Romer
began writing two years ago did not look like something that could
determine the outcome of a Super Bowl. Sure, it was an analysis of
whether professional football teams punt more often than is
rational, but it seemed intended mainly for the amusement of sports
fans who happen to be professors.

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Professor Romer, an economist at the University of California at
Berkeley, used the phrases "Bellman equation" and
"dynamic-programming analysis" - in the paper's title, no less. His
footnotes cited work published in Econometrica, Cognitive Science
and other publications that are not exactly must-reads in N.F.L.
locker rooms.

But when his conclusion - teams punt too much - began getting
attention last summer, a reporter asked Bill Belichick, the coach of
the New England Patriots, about the paper.

"I read it," he said, according to The Boston Herald. "I don't
know much of the math involved, but I think I understand the
conclusions and he has some valid points."

Upon hearing that, Professor Romer's jaw dropped, he said. His
paper was available only on his Berkeley Internet site,
emlab.berkeley.edu /users/dromer, and the site of a group called the
National Bureau of Economic Research.

But the most interesting development was yet to come. Two weeks
ago, facing a fourth down in the Patriots' own territory on the very
first drive of the game - a sure punting situation in the N.F.L. -
Belichick decided to go for a first down and made it. The Patriots
soon scored a touchdown and were on their way to today's Super Bowl,
against the Carolina Panthers.

Football analysts immediately called the decision an instance of
a coach's instinct triumphing over cold analysis. In fact, Professor
Romer said last week, Belichick seemed to be "throwing gut instinct
out the window and going on analysis." The information is right
there in Figure 5 of the economist's paper: on fourth and 1 on your
own 44-yard line, the potential benefit of keeping the drive going
outweighs the cost of giving the opponents good field position.

The coach may not have not been thinking about Professor Romer's
paper at that moment, but he has clearly adopted the methods of a
social scientist in a way that few other sports coaches have.
Belichick, who majored in economics at Wesleyan University,
approaches his job much the way a financial analyst pores over a
balance sheet. He seems to view every decision as a chance to
perform better cost-benefit analysis than his peers do. Richard
Miller, a Wesleyan economist with whom the coach remains in touch,
calls the approach "incremental analysis." In plain English, it
involves looking for subtle differences in one small area that can
affect an entire system, whether that system is a company, a stock
market or a football game.

Consider the Patriots' behavior when they need just a couple of
yards for a first down or a touchdown. No other team ran the ball
more often in those situations this season, according to Football
Outsiders, an Internet site that analyzes statistics, even though
the Patriots are considered to have one of the weaker running games
in the league.

The numbers still favor the strategy because running is far more
effective in gaining a few yards than passing is. Yet many other
teams including the Giants and Jets, which together won four fewer
games than New England this year, tried many ineffective pass plays,
in an effort to surprise the defense. It's a little like surprising
your opponent in chess by letting him capture your queen.

Belichick also seems to understand an idea that economists call
"hyperbolic discounting," which holds that people tend to place too
much value on the here and now. Taking advantage of this, the team
made two trades during last year's draft that essentially swapped a
lower pick in 2003 for a higher one in 2004, noted Aaron Schatz, the
editor of Football Outsiders. The Patriots will now enter this
spring's draft holding many more high picks than a Super Bowl team
typically does.

And Professor Romer's paper is not the only ivory-tower research
that has made its way into the coach's head. After Harold
Sackrowitz, a Rutgers statistician, was quoted in The New York Times
and elsewhere saying that teams try for a two-point conversion too
often after scoring a touchdown, he received a call from Ernie
Adams, the Patriots' football research director and a friend of Mr.
Belichick's since they attended Phillips Academy in Andover, Mass.,
together. The research director sent Professor Sackrowitz a copy of
the team's chart telling coaches when to go for two points, and the
statistician critiqued it. "Nobody had any real interest other than
the Patriots," said Professor Sackrowitz, who now roots for them in
addition to the Giants and Jets. New England did not try a single
two-point conversion this year.

In the end, none of these moves is nearly as important as
designing a defensive strategy or drafting good players. But
Belichick's hyper-efficient approach almost certainly gives his team
a small advantage in a game that can easily be decided by minor
differences.

The approach has also altered the course of Professor Romer's
research. When talking about the Berkeley economist's paper this
year, Belichick noted that it did not consider the emotional effect
that failing on fourth down could have on a team.

Once Professor Romer read that, he ran the analysis again to see
whether teams performed worse after being stopped on fourth down.
They did not, just as most economists would expect. Come tomorrow,
when Belichick will have some time on his hands, he can read the
details on the professor's Web site.